The invention relates to an arrangement for suppressing over-voltage peaks on conductors, especially power line conductors, leading into an electronic apparatus provided with a closed electrically conducting surface; and more particularly to such an arrangement in which, arranged in a housing, there are voltage-limiting elements connected between the lines mutually and similar elements connected between the lines individually and a common reference point, preferably the housing, together with lowpass filters consisting of series inductances and parallel capacitances.
Overvoltage peaks on lines can stem from various causes. In the case of power supply lines in particular, such peaks result from switching transients produced by other connected users or by the effects of lightning. Because of the different causes, overvoltage peaks of different shape or waveform are normally generated, and those with steep leading edges are the most difficult to suppress since the actuation of practically all voltage-limiting devices takes place with a certain delay. Particularly critical in this respect are overvoltage peaks generated by NEMP, i.e. by nuclear electromagnetic pulses caused by explosions at a great height. Such overvoltage peaks have edge steepnesses of less than 10 ns at very high energies. If such overvoltage peaks are not adequately suppressed, they can cause considerable damage in electronic apparatus built up from modern semiconductor components.
For the suppression or reduction of overvoltage peaks it is common practice to use voltage-limiting components in combination with lowpass filters consisting of series inductances and parallel capacitances. Normally a combination of this kind is used for each line. In the case of overvoltage peaks with very steep edges, such as those triggered by NEMP, the speed of response of conventional voltage-limiting devices is insufficient, however, to achieve a limitation of the overvoltage peaks to values that can be tolerated by modern semiconductor components, at the output of a combination consisting of a voltage-limiting component and a lowpass filter. An improvement could be achieved by connecting several of such combinations in series, but in that case high-frequency coupling between input and output would make it difficult to achieve adequate limitation of the overvoltage peaks.